Your question is not clear, but I will try to help.
Draw a circle and any chord in the circle.
Now draw 3 more lines.
Draw the radii to the points at the end of the chord and through the midpoint of the chord.
You should see that you have 2 congruent right triangles...which verifies that the perpendicular bisector of the chord passes through the center of the circle.
Now if you clarify your question, I think you should be able to answer it.